1. Technical Field
This disclosure relates generally to surgically implanted physiological shunt systems and related flow control devices. More particularly, the present disclosure relates to a position indicator and adjustment tool for such shunt systems having variable pressure settings for the one-way flow control valves controlling the flow of Cerebral Spinal Fluid (CSF) out of a brain ventricle and preventing backflow of fluid into the brain ventricle.
2. Description of Related Art
A typical adult has a total of about 120-150 cubic centimeters (cc) of CSF with about 40 cc in ventricles in the brain. A typical adult also produces about 400-500 cc/day of CSF, all of which is reabsorbed into the blood stream on a continuous basis.
Sometimes, the brain produces excess CSF or there can be a blockage of the normal CSF pathways and or absorption sites resulting in a condition known as hydrocephalus. Hydrocephalus is a condition of excessive accumulation of CSF in the ventricles or brain tissue. Hydrocephalus can result from genetic conditions, congenital defects infection, cancer, hemorrhage trauma to the brain or as a person ages.
Excessive accumulation of CSF, due to hydrocephalus or other causes, manifests itself as increased pressure within the brain. Whatever the cause, over time, this increased CSF pressure causes damage to the brain tissue. It has been found that relieving the CSF pressure is therapeutically beneficial. This relief is usually performed by draining CSF from the ventricles.
Patients with hydrocephalus normally require, at least over some time period, continuous drainage of excess CSF to maintain normal CSF pressure in the brain. Excessive CSF accumulated in the ventricles of the brain is typically drained away from the brain using a shunt system.
Where hydrocephalus is a chronic condition, the shunt system typically drains the CSF into the patient's peritoneal cavity or into the patient's vascular system. Such shunt systems typically have a catheter implanted in the ventricle of the brain. The catheter is connected to a fluid control device which is in turn connected to a catheter which empties in to the patient's peritoneal cavity or into the patient's vascular system. An example of a fluid control device is shown in U.S. Pat. No. 5,637,083 issued to William J. Bertrand and David A. Watson on Jun. 10, 1997 entitled “Implantable Adjustable Fluid Flow Control Valve”, the teaching of which is incorporated herein in its entirety by reference. Current fluid control devices include an inlet connector, an outlet connector and a valve positioned between the inlet connector and the outlet connector. The valve includes a mechanism to control fluid flow through the valve. In some instances, the mechanism includes a magnet embedded within the valve. Rotating a rotor or otherwise shifting of the rotor position changes the internal configuration of the mechanism. Changing the internal configuration of the mechanism produces a variety of pressure or flow characteristics for the valve. As the internal configuration of the valve changes, the pressure or flow characteristics of the valve change.
In use, the valve is subcutaneously placed on the patient's skull. The catheter going to the patient's ventricle is attached to the inlet connector. The catheter going to the patient's peritoneal cavity or vascular system is attached to the outlet connector. In this way, a direction of flow is established from the inlet connector through the valve to the outlet connector. Changing the internal configuration of the mechanism by coupling the external magnet to the internal magnet and rotating the external magnet effects a movement internal to the shunt and produces a variety of pressure or flow characteristics through the valve.
It is desirable to have a number of different settings in order to achieve different pressure and/or flow characteristics of the valve. One complication with current adjustable valves is that once implanted, it is difficult to determine the setting of the valve and/or adjust the setting of the valve. Having more settings for the valve only makes determining and/or adjusting the valve setting more difficult. With some adjustable valves, x-ray images are used to determine the current state or post adjustment state of the valve. By requiring an x-ray, it is time consuming and costly to determine and adjust the valve setting, as well as not being in the best interest of the patient due to x-ray exposure issues.
Another complication with current adjustable valves is compatibility with magnetic resonance imaging (MRI) procedures. As many current adjustable valves utilize magnets for adjusting and/or determining a valve setting, their function can be disrupted due to interaction of magnetic components in the valve with the applied magnetic field created during the MRI procedure. In particular, the valve setting can be altered to a random, undesirable setting. If the valve setting is not returned to the desired setting after the MRI procedure, this situation can be extremely harmful to a patient. As such, the valve setting needs to be immediately reset to the desired setting upon conclusion of the MRI procedure. In any event, improvement of valves for the treatment of hydrocephalus can provide great benefit.